The present invention relates to a multi-layer circuit board and a method for making a multi-layer circuit board and more particularly, to a method for making a multi-layer electrical circuit board having at least one electrically conductive interconnection portion or xe2x80x9cviaxe2x80x9d which selectively allows various portions and/or components residing within the electrical circuit board to be electrically and operatively connected and which further includes selectively formed air-bridges which increase the amount or density of the contained electronic components.
Multi-layer circuit boards allow electrical and/or electronic components to selectively and operatively populate opposed surfaces of each board (or other respective interior portions of each of the boards), thereby desirably allowing each of the electrical and/or electronic circuit boards to contain a relatively large amount of electrical components which efficiently and densely populate the respective boards. It is desirable to allow each of the component-containing surfaces or portions of a created and/or formed electrical and/or electronic circuit board to communicate and/or to be selectively interconnected, thereby allowing the contained electrical components to cooperatively and selectively form one or more desired electrical circuits. This desired communication and/or interconnection typically requires the use of shared electrical ground planes, the transmittal of electrical power and/or control type signals between each of the component containing surfaces or board portions, and/or the connection of components which respectively reside on opposed surfaces and/or within diverse portions of the formed electrical circuit board.
This desired interconnection typically requires that one or more holes be drilled within each of the circuit boards, thereby physically creating at least one xe2x80x9cthrough holexe2x80x9d or xe2x80x9cviaxe2x80x9d which extends through at least some of the opposed component containing surfaces and through at least some of the various interior circuit board portions. Such drilling is undesirable since it is relatively time consuming, costly, potentially causes damage to significant numbers of the formed electrical circuit boards requiring these circuit boards to be destroyed, and requires costly and inefficient electroless and/or electrolytic plating of the formed holes or xe2x80x9cviasxe2x80x9d.
While some attempts have been made to obviate the need for such plating, such as by the use of a conductive epoxy within each of the drilled holes, these attempts have not produced reliable electrical interconnections and these produced interconnections are not typically adapted to allow the communication of electrical power signals between the board surfaces. The produced apertures also do not securely and reliably receive a component.
Further, it is desirable to form xe2x80x9cair-bridgesxe2x80x9d or xe2x80x9ccrossover type circuitsxe2x80x9d upon one or more selected surfaces and/or within certain component containing portions of the formed circuit board in order to allow multiple levels of circuits and/or electrical interconnections to be formed upon a single board surface or within a certain component containing portion of the circuit board, thereby desirably increasing the amount of electrical circuits which may be created upon and/or within the created circuit board (i.e., increasing the electrical circuit density).
These prior circuit board creating methodologies create and/or form air-bridges and crossover circuits which do not typically and efficiently accommodate certain desirable circuit board interconnection processes and/or schemes such as and without limitation, the use of relatively heavy wire bonding (e.g., using aluminum wire having a diameter of about five thousandths of an inch to about twenty thousandths of an inch) or the direct connection of components to a surface of the board.
There is therefore a need to provide a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated drawbacks of prior electrical circuit boards and/or board forming methodologies, which selectively allows for the efficient creation of interconnection portions which traverse the various layers of the formed electric circuit board assembly, and which further allows for the efficient and selective formation of air-bridge members or crossover members which desirably accommodate diverse types of circuit interconnection processes.
It is a first object of the present invention to provide a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated drawbacks of prior multi-layer electrical circuit board forming methodologies and techniques.
It is a second object of the invention to provide a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated drawbacks of prior multi-layer electrical circuit board forming methodologies and techniques, which allows the formed circuit board to receive various contained electronic components, which allows for the selective, efficient, and reliable formation of electrically conductive interconnection portions which selectively and cooperatively allow for communication and/or electric connection by and between at least some of these various electronic components.
It is a third object of the invention to provide a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated drawbacks of prior multi-layer electrical circuit board forming methodologies and techniques and which allows for the selective and efficient formation of air bridges and/or crossover members which are adapted to accommodate a wide variety of component interconnection assemblies.
According to a first aspect of the present invention, a method for making an electric circuit board is provided. The method includes the steps of providing a first member having a first and a second surface; attaching a layer of a first material to the second surface of the first member; removing at least one portion of the first member, thereby creating at least one aperture within the first member and at least one exposed portion of the first material; filling the at least one aperture with a second material; providing a first pre-circuit assembly having a first core portion which is operatively contained between a second member and a third member, and a second pre-circuit assembly having a second core portion which is operatively contained between a fourth member and a fifth member; attachably overlaying the third member upon the first surface of the first member and the second material and attachably overlaying the fourth member upon the first material, thereby creating a third pre-circuit assembly; selectively forming at least one aperture through the third pre-circuit assembly; selectively forming at least one aperture through said first pre-circuit assembly; removing at least one portion of the core portion within the first pre-circuit assembly and removing at least one portion of the core portion within the second pre-circuit assembly, thereby forming at least one cavity within the first pre-circuit assembly and at least one cavity within the second pre-circuit assembly; filling the at least one cavity within the first pre-circuit assembly and the at least one cavity within the second pre-circuit assembly with the second material; and applying a third material to the second member and to the fifth member, thereby creating a circuit assembly.
According to a second aspect of the present invention, a circuit assembly is provided. The circuit assembly is made by the process of providing at least one electrically conductive member; selectively etching that at least one electrically conductive member; providing at least one pre-circuit board having a core portion which is operatively contained between top and bottom members; attaching the pre-circuit board to at least one electrically conductive member; and selectively removing portions of the core, thereby creating a multi-layer circuit board having at least one air-bridge.
These and other objects, aspects, and advantages of the present invention will become apparent upon reading the following detailed description in combination with the accompanying drawings.